The throttling process of a control valve produces sound that is often at levels too loud for surrounding personnel. To reduce this noise level, control valves sometimes include specially-designed throttling trim in the lower portions of the valve cage. The trim typically uses small flow passages, which may be tortuous. The passages are used to shift frequencies and, if tortuous, to reduce velocities and, hence, amplitude. Because of the resultant higher frequencies, and possibly lower amplitude, the noise level is reduced.